1. Field of the Invention
This invention relates to formulations and methods for preserving sensitive biologicals, viruses, bacteria and eukaryotic cells by drying. More particularly, the invention relates to preservation mixtures comprising viruses or cells and protectants, wherein the mixtures are adapted to stabilize these samples during dehydration and subsequent storage at ambient and higher temperatures.
2. Description of the Related Art
Sensitive biomolecules, viruses, bacteria, vectors, eukaryotic cells, and small multicellular specimens have a broad range of uses, including for example, human and veterinary pharmaceuticals, immunizations and vaccines, molecular biology, gene therapy, as well as in the food industries. Typically, these bioactive materials, viruses and cells are active in aqueous environments; thus, conventional formulations of such samples have been in aqueous solutions. However, many bioactive materials, particularly viruses and cells, are sensitive to degradation and loss of activity and/or viability in aqueous solutions, particularly at ambient or higher temperatures. Accordingly, such samples often require refrigeration or have short shelf lives under ambient conditions.
Bioactive materials, viruses and cells can be destroyed via a number of chemical mechanisms known in the art. Water is a reactant in nearly all of these destructive pathways. Further, water acts as a plasticizer, which allows unfolding and aggregation of proteins. Since water is a participant in almost all degradation pathways, reduction of the aqueous solution or suspension of bioactive materials, viruses and cells to a dry powder provides an alternative formulation methodology to enhance the stability of such samples. Viruses and cells can be dried using various techniques, including freeze-drying, foam-dying, spray-drying and dessication. Aqueous solutions of biomolecules, viruses and cells are dried and stored as dry powders until their use is required.
In addition to dehydration, vitrification represents another significant approach to preservation (stabilization) of sensitive biomolecules, viruses, and cells. Vitrification can be achieved in the dry state at ambient temperatures, as well as in an aqueous environment under cryogenic conditions (freezing). Ambient temperature stability in the dry state is extremely desirable for many reasons, including storage convenience and economics, transportation, flexibility of delivery options, applicability to emergency situations and access to third world countries. Consequently, vitrification of biomolecules, viruses and cells in the dry state is particularly desirable. However, drying of unprotected biomolecules, viruses and cells, like freezing of such samples, may be very damaging. Therefore, there is a need to develop preservation mixtures in which biomolecules, viruses and cells can be dehydrated and vitrified with minimum loss of their activity or viability.